A clothing manufacturer estimates from past quality control inspections that 4.8% of sweatshirts produced are irregular. If an inspector randomly selects 650 sweatshirts, estimate the probability that at least 30 are irregular.

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- Oct 22nd 2010, 11:30 AMterminatorthe normal approximation
A clothing manufacturer estimates from past quality control inspections that 4.8% of sweatshirts produced are irregular. If an inspector randomly selects 650 sweatshirts, estimate the probability that at least 30 are irregular.

- Oct 22nd 2010, 01:03 PMmr fantastic
- Oct 22nd 2010, 05:22 PMterminator
np = 350x0.10 = 35

n(1-p) =350 x 0.90 = =315

np>=5, n(1-p) >=5

Therefore, the approximation is resonably close to a normal distribution because

np <= 5 and n(1-p) >=5

Now I can calculate the standard deviation

mean = np =35

sd= sqr(npq) =5.61

How do I calculate the probability?

**"In mathematics, you don't understand things. You just get used to them." -- Johann von Neumann** - Oct 22nd 2010, 09:34 PMmr fantastic
- Oct 23rd 2010, 05:09 AMterminator
Thanks mr.Fantastic - you're a nice man

"In mathematics, you don't understand things. You just get used to them." -- Johann von Neumann